Dianthus deltoides L.

Maiden Pink

Dianthus deltoides is a striking plant of thin, basic to slightly acid soils on open and sunny slopes in unimproved grasslands and heaths. The deep-pink, scentless flowers have spotted petals with a dark bar or zigzag at the base, and the calyx is soft to the touch due to the presence of downy hairs. In Britain its native range is obscured by garden escapes but covers much of England, Wales and eastern and central Scotland. It is probably not native in south- west England and Ireland. The species was assessed as Near Threatened in both Wales and Great Britain, but as Vulnerable in England due to substantial declines in distribution and range. ©Heide Nelke

IDENTIFICATION 2009). All leaves have a prominent mid-rib, stomata on both sides, and rough margins fringed with short hairs (Poland & Dianthus deltoides is a loosely tufted perennial producing Clement 2009). few-flowered (often solitary) inflorescences held on rounded, shortly pubescent stems (5-)15-30(-45) cm tall with ±swollen nodes (Jonsell 2001). The striking rose-red (-pink or white), SIMILAR SPECIES scentless flowers (12-20 mm) have petals that are usually D. armeria flowers are surrounded by an involucre of leaf-like spotted with a dark bar or zigzag at the base of the petal-limb, bracts (Stace 2010). This character is absent in D. deltoides. which itself is divided <1/4 way to the base into narrow or D. gratianopolitanus has glabrous stems, scented flowers and triangular teeth (Jonsell 2001; Stace 2010). The calyx (12-18 unspotted petal-limbs that do not carry a dark bar. Cultivars mm long) and epicalyx scales (about half as long as the calyx) of D. deltoides usually have a more robust and compact are soft to the touch due to the presence of downy hairs. appearance and larger flowers (Jonsell 2001). Epicalyx scales are abruptly pointed and have a wide papery margin (Jonsell 2001). Leaves of vegetative shoots are linear –oblanceolate, subacute or obtuse, 8-20 (-30) × 1-4 mm, HABITATS whereas the leaves of flowering stems are linear-lanceolate, Dianthus deltoides is found in dry and open habitats on basic acute and up to 40 mm (Jonsell 2001; Poland & Clement to mildly acid soils derived from Silurian sandstones, basalt, mica-schist, Carboniferous limestone, chalk, and thin soils associated with past quarrying or lead mining activities (e.g. metalliferous spoil in Bradford Dale, Derbyshire) (Braithwaite 1994; Lusby 2002). Plants are often confined to steep slopes or banks with a sunny aspect within unimproved sandy grassland, heaths, dune slacks, dry calcareous grassland, and road verges as cliff ledges amongst rocky outcrops (e.g. Arthur’s Seat in Edinburgh). In parts of Europe and Russia, D. deltoides is also associated with Molinia-meadows on calcareous peat soils where it grows with Cirsium dissectum, Succisa pratensis and Viola persicifolia.

Dianthus deltoides growing in acid grassland on volcanic rock outcrops at Banc Hirllwyn SSSI, Radnorshire. ©John Crellin, June 2009.

Dianthus deltoides L.

The flowers are protandrous, with pollen-bearing anthers presented two days before a pistil of two styles protrudes from BIOGEOGRAPHY the flower for an additional 1.5 days (Jennersten 1988). In Great Britain D. deltoides is scattered throughout England, Flowers close each night and so can only be pollinated by Wales, central and eastern Scotland and the Scottish borders, diurnal insects. The relatively long, narrow and tough calyx but is absent from south-west England, western and northern tube and pink petal-limbs are characteristic of butterfly- Scotland and Ireland. It is a mainly lowland but is found up to pollinated flowers adapted to exclude short-tongued insects 355 m at Parsley Hay, Derbyshire. Its distribution has become (Faegri & van der Pijl 1979). Studies in southwest Sweden severely fragmented in recent times, with for example have shown that butterflies are important pollinators England experiencing a decline of 39% since 1930 (Stroh et al. (Jennersten 1984) and synchrony between the phenology of 2014), and as such populations are now largely confined to D. deltoides and Thymelicus lineola (Essex Skipper) and small refugia (Braithwaite 1994). Cultivars of D. deltoides are Ochiodes venata (Large Skipper). found as naturalised garden escapes across Scotland, Wales, Dianthus deltoides can produce over 60 obovate seeds (2 mm England and Ireland, with the range of native plants and alien long) per capsule, although Jennersten (1988) demonstrated a cultivars occasionally overlapping (Lusby 2002). significant relationship between visitation rates by pollinators Dianthus deltoides is widespread throughout much of central, and seed set, with fragmented populations of D. deltoides eastern and northern Europe but becomes increasingly having much lower seed set due to a lower diversity and uncommon towards the south and west (Jalas & Suominen abundance of both flowering plants and flower-visiting 1985). Its eastern range extends through Russia as far as Lake insects. Upon maturity, dry capsules are shaken by the wind Baikal, with its most northerly native limits extending to and eventually release seeds close to the parent plant, with Tromso and Sør-Varanger in Norway (Jonsell 2001). D. germination and the subsequent establishment of young deltoides is present as a non-native in North America, New plants dependent on the availability of suitable safe sites in Zealand and Australia. open areas. Seedlings and young plants in particular require open, warm conditions.

ECOLOGY An over-wintering perennial chamaephyte of sunny, dry THREATS habitats on basic to mildly acid soils (Hill et al. 2004), Cessation of grazing can lead to a rank sward and the eventual flowering from June to September, reproducing by seed and loss of D. deltoides. However, over-grazing leading to a also via creeping vegetative shoots. closed, short sward is also undesirable and in the long-term can result in the loss of populations. Habitat loss via conversion of sites to other uses such as intensive pasture or forestry has substantially reduced the number and connectivity of sites. Fragmentation and subsequent reduced seed set should also be considered as future threats to extant populations.

MANAGEMENT Ideal management involves either a late-summer cut, removal of arisings, and aftermath grazing, or livestock grazing, preferably with cattle, throughout the spring and summer but with reduced levels in the summer months. However, meadow restoration trials conducted by Hellström et al. (2007) in northern Finland found that a mowing/disturbance regime in late summer led to the establishment of D. deltoides into a sown sward by providing bare soil and open ‘micro- sites’ for germination. This management regime created similar conditions to traditional practices of late mowing and aftermath cattle grazing, and can be viewed as a suitable alternative if cattle are not available in the locality.

REFERENCES Braithwaite, M.E. 1994. Dianthus deltoides L. Maiden Pink. In: A. Stewart, D.A. Pearman & C.D. Preston (eds) Scarce Plants in Britain, p.137. JNCC, Peterborough. Distribution of Dianthus deltoides in Great Britain and Ireland.

Dianthus deltoides L.

Faegri, K. & van der Pijl, L. 1979. The Principles of Pollination Lusby, P.S. 2002. Dianthus deltoides (L.) Maiden Pink. In: Ecology. Pergamon Press, Oxford. C.D. Preston, D.A. Pearman, & T. Dines (eds) New atlas of the British and Irish flora, p.181. Oxford University Press, Hellström, K., Huhta, A.P., Rautio, P. & Tuomi, J. 2009. Seed Oxford. introduction and gap creation facilitate restoration of meadow species richness. Journal for Nature Conservation Poland, J. & Clement, E. 2009. The Vegetative Key to the 17: 236-244. British Flora. Botanical Society of the British Isles, London. Hill, M.O., Preston C.D. & Roy D.B. 2004. PLANTATT. Stace, C. A. 2010. New Flora of the British Isles, third edition. Attributes of British and Irish Plants: Status, Size, Life Cambridge University Press, Cambridge. history, Geography and Habitats. NERC Centre for Stroh, P.A., Leach, S.J., August, T.A., Walker, K.J., Pearman, Ecology and Hydrology, Monks Wood, Huntingdon. D.A., Rumsey, F.J., Harrower, C.A., Fay, M.F., Martin, J.P., Jalas, J. & Suominen, J. (eds) 1985. Atlas Florae Europaeae. Pankhurst, T., Preston, C.D. & Taylor, I. 2014. A Vascular 6. Caryophyllaceae (Alsinoideae and Paronychioideae). Plant Red List for England. Botanical Society of Britain and Committee for Mapping the Fiora of Europe & Societas Ireland, Bristol. Biologica Fennica Vanamo, Helsinki.

Jennersten, O. 1984. Flower visitation and pollination AUTHOR VERSION efficiency of some North European butterflies. Oecologia Peter Stroh. Version 1: 04 November 2014. 63:80-89.

Jennersten, O. 1988. Pollination in Dianthus deltoides SUGGESTED CITATION (Caryophyllaceae): effects of habitat fragmentation on visitation and seed set. Conservation Biology 2: 359-366. Stroh, P.A. 2014. Dianthus deltoides (L.) Maiden Pink. Species Account. BSBI. Jonsell, B. (ed.) 2001. Flora Nordica 2. The Royal Academy of Sciences, Stockholm.